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[DPRG] Motor backlash / Back EMF
Subject: [DPRG] Motor backlash / Back EMF
From: DeltaGraph at aol.com
DeltaGraph at aol.com
Date: Tue Jan 8 01:39:14 CST 2008
Hey Chuck,
Thanks for more explanation.
I found your ASCII art worked good once went to non-proportional font.
Will read again.
I fired up LTspice/SwitcherCAD and figured out how to use the program sort
of.
I think I am seeing ground bounce as you describe it with ground connected
as shown.
I have turned off (via large resistors) most of the capacitive filtering in
the example circuit.
I am clamping (to some extent) the flyback of the motor inductor, but the
ground inductance is allowed to generate a voltage which counters MCU supply by
pushing "ground" up -- if I said that correctly.
Here are pics of schematic and plot...
http://_www.deltagr.com/dprg/DualBatMotorSwitch.jpg_
(http://www.deltagr.com/dprg/DualBatMotorSwitch.jpg)
_http://www.deltagr.com/dprg/MotorSim.jpg_
(http://www.deltagr.com/dprg/MotorSim.jpg)
Ignore first cycle on graph -- not sure why not doing correct analysis on
that -- told it something...
My schematic is prettier than yours!, but I just spent TOO much time
figuring out how to use the simulation tool again.
I know simulation is only as good as person designing it, but I have learned
a good deal I think.
I can see grounds with large inductances can produce some pretty wicked
voltages -- if I was doing things right. Without capacitor filter -- some pretty
wicked voltages... looks like one could toast a MOSFET ....
Hope I am getting it...
Ron
**************Start the year off right. Easy ways to stay in shape.
http://body.aol.com/fitness/winter-exercise?NCID=aolcmp00300000002489
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